Audio comes and goes in ANY file in ANY player

Lately I got a really annoying problem.
When plying a video file in WMP or VLC, there suddenly is a “screetching” sound and or “thumps”, and then the sound is gone.
The video plays fine, and then after a few minutes the “screetch/thump” is on again, and the movie sound may or may not come back!

I’ve tried different file types and players and even different speaker systems, but with the same result.
I was on my way to throw the sound card in the bin when I made the following interesting? observation:

Restarting the file in the SAME player will not make any difference at all, but starting the file in a DIFFERENT player will always mean that the sound is on. This way I can get through a movie by alternating media players, say 20-25 times.

Knowing that this sounds like mumbo-jumbo to a n00b like myself, my only hope is that someone out there reads this and goes: “HA, this is easy!"